1. Field of the Invention
The present invention is directed to new and improved granular material transmission means for feeders for welding, cladding, overlaying and the like, and particularly apparatus wherein granular or powdered alloy materials for producing an alloy weld are fed and deposited in desired amounts on the area to be fusion welded or weld overlayed and the like which provides an alloy weld of a predetermined composition.
2. Description of the Prior Art
Due to the difficulty of providing homogeneous mixtures to the weld zone, a major problem in fusion welding or weld overlaying is the provision of alloy welds of uniform composition or analysis. For example, premixing of metals does not consistently provide homogeneous mixtures to the work because the heavier metal particles settle out; the larger particles rise to the surface; and the more angular particles rise to the top in storage, transportation or other movement. The same problem exists in premixing flux.
In the process of performing bulkwelding or thermal or plasma spraying, it is either desirable or necessary (depending on the operation) to feed powder to the welding means so that a cross section of the powder stream at any point contains the proper percentages of each ingredient to give the desired analysis to the weld being deposited. Also, it is either desirable or necessary that the rate of flow of these powders be uniform so as to avoid plugging the apertures through which the powder has to flow or overloading momentarily the heating means for melting the powder and causing voids in the welds. In a premixed powder, the blend will be uniform if (1) the particles are in the same general area of size; (2) the particles are either all angular or all round; and (3) the particles are in the same area of density. Otherwise, the large particles and the angular particles rise and the round particles and the heavy particles sink, giving a non-uniform analysis to the weld. The same problems exist in premixing flux materials, as used in open arc or submerged arc welding.
The provision of a feeder which uniformly feeds homogeneous mixtures of metal alloy materials to the work and by which a fusion weld or weld overlay is obtained of uniform composition or analysis in either open arc, submerged arc, submerged or gas-shielded welding has been highly desirable. It would also be desirable to simultaneously feed materials in desired uniform amounts so that uniform accurate, predetermined, homogeneous mixtures are obtained and fed to the weld zone without any special or expensive processing or premixing of the various metals. It would be desirable to provide a feeder capable of uniformly feeding a variety of materials, such as non-compatible materials, to the weld zone simultaneously, without any unwanted slugs or globules of agglomerated particles entering the weld zone.
In the usual metering equipment for bulk-welding (my U.S. Pat. Nos. 3.060 307 and 3,179,991), feeding is accomplished by a wheel (or wheels) which contain pockets on the periphery, and which pockets dump their contents at short intervals while the wheel turns. Thus, the feeding of material is in short batches (or slugs) in an intermittent manner. This feeding can overload the orifices through which the powder must pass as well as momentarily overloading the powder melting means as described above.
My copending application Ser. No. 657,434 filed Oct. 3, 1984, is directed to a multiple feeder apparatus for welding which has a plurality of material feeding elements, each of which feeds weld material from a material-containing hopper to feed tubes which transmit the weld material to a single tube feeding into a weld material distributor. Slugs of weld material can pass from the hoppers to the weld zone, adversely affecting the weld deposit and final welding product.